Olefin conversion

ABSTRACT

Olefins are converted into other olefins having different numbers of carbon atoms by contact with a catalyst comprising a silica support containing tungsten oxide and a promoting amount of at least one titaniferous agent and activated under conditions suitable for the titaniferous agent to promote the activity of tungsten oxide and silica for the disproportionation and isomerization reaction.

BACKGROUND OF THE INVENTION

This invention relates to the conversion of olefins according to theolefin reaction, to catalysts therefore and to a method for modifyingthe activity of such catalysts. In accordance with one aspect, thisinvention relates to a catalyst comprising tungsten, silica and at leastone titaniferous agent or component suitable for use in thedisproportionation and isomerization of olefins.

In accordance with another aspect, this invention relates to a catalystsuitable for use in the disproportionation and isomerization of olefinscomprising silica and tungsten promoted with at least one titaniferousagent or component.

In accordance with another aspect, this invention relates to a processfor the disproportionation and isomerization of olefinic hydrocarbonswith a disproportionation catalyst modified as hereinbefore describedunder conditions of temperature and pressure which effectdisproportionation and isomerization of olefinic hydrocarbon feeds.

The disproportionation or metathesis of olefins is a reaction in whichone or more olefinic compounds are transformed into other olefins ofdifferent molecular weights. The disproportionation of an olefin withitself to produce an olefin of a higher molecular weight and an olefinof a lower molecular weight can also be referred to as aself-disproportionation. For example, propylene can be disproportionatedto ethylene, and cis-, and trans-2-butene.

Another type of disproportionation involves the cross-disproportionationof two different olefins to form still other olefins. An example wouldbe the reaction of one molecule of 2-butene with one molecule of3-hexene to produce two molecules of 2-pentene.

By the term "disproportionation" or "metathesis" throughout thespecification is meant the conversion of the feed olefinic (orunsaturated) hydrocarbon to a mixture of olefinic (or unsaturated)hydrocarbons having different numbers of carbon atoms than the feedhydrocarbons.

Among the catalysts that have been developed for disproportionation arethose comprising silica containing a catalytic amount of tungsten oxide.The present invention is based upon the discovery of a way to improvethe activity of such a catalyst for the isomerization of olefins.

Previously it has been found that the activity of olefin reactioncatalysts, e.g. disproportionation or metathesis catalysts, can bemodified by admixture with a double bond isomerization catalyst. Forexample, mixtures of olefin reaction catalysts with magnesium oxide orzinc oxide are particularly effective in increasing conversion and/orwidening the spread of products.

It has now been found that the isomerization activity of an olefinreaction catalyst, i.e. a disproportionation or metathesis catalyst, canbe modified by treating the catalyst with a titaniferous agent.

Accordingly, an object of this invention is to provide a method for theconversion of olefins.

Another object of this invention is to provide a catalyst for theconversion of olefins.

Still another object of this invention is to provide a method forconverting olefins to olefins having different numbers of carbon atomsfrom the feed hydrocarbons.

Still another object of this invention is to provide a method formodifying the activity of a disproportionation catalyst for theisomerization of olefins.

Other aspects, objects, and the several advantages of the invention willbe apparent to one skilled in the art upon reading the disclosureincluding a detailed description of the invention and the appendedclaims.

SUMMARY OF INVENTION

In accordance with the present invention, a disproportionation(metathesis) catalyst comprising silica containing a catalyticallyeffective amount of tungsten is improved with respect to isomerizationactivity by contacting the catalyst with a promoting amount of at leastone titaniferous agent or component under conditions suitable for thetitaniferous agent to promote the isomerization activity of thetungsten-silica catalyst.

Further, in accordance with a specific embodiment of the presentinvention, a disproportionation (metathesis) catalyst comprising silicacontaining a catalytically effective amount of tungsten is modified byincorporating a promoting amount of least one titaniferous compound andthen activating by heating under calcination and, optionally, reducingconditions suitable for the titaniferous compound to promote theisomerization activity of the tungsten-silica catalyst.

Also according to the invention, a process is provided for thedisproportionation and isomerization of an olefinic hydrocarbon bycontacting the same with a disproportionation catalyst modified ashereinbefore described under conditions of temperature and pressurewhich effect disproportionation and isomerization of the feed.

DESCRIPTION OF SPECIFIC EMBODIMENTS

The silica component of the catalyst can be any conventionalcatalyst-grade silica. Some examples are: precipitated silica gel,microspheroidal silica, flame hydrolyzed silica, and silica aero-gels.These materials have appreciable suface area, usually in the range of50-700 m² per g and can range from fine powders to course granules.These materials often contain small amounts of compounds of aluminum andof sodium in the order of a few tenths of a percent by weight andsmaller. Trace amounts of other metals and such small amounts of thesematerials are acceptable.

The tungsten component of the catalyst of the invention can beincorporated into the silica support by any suitable method including,for example, impregnation, dry mixing, and coprecipitation. Tungstenoxide can be added directly or in the form of a tungsten compound thatcan be converted to the oxide by calcination.

Generally the finished catalyst contains from about 0.1 to about 30percent by weight of the tungsten component calculated as the metaloxide and based on the total weight of the tungsten component and thesilica component, although larger amounts can be used. In most instancesa proper amount of the promoter is from about 1 to about 20 percent.Excellent results have been obtained with silica-based catalystscontaining from about 2 to about 15 percent by weight of tungsten oxide.

The solid component of the catalyst can be in any conventional catalyticshape or size depending upon the type of conversion in which it is to beutilized. For example, in fixed-bed catalyst systems the solid compositecan be in the form of spheres, pellets, extrudates, agglomerates, andthe like. In slurry-catalyst systems, the solid can be in the form ofrelatively small particles or in the form of a powder.

According to the invention, a tungsten-silica olefin reaction catalystis modified by the inclusion of a titaniferous compound deposited on thesurface thereof. The titaniferous compound is deposited on the surfaceof the catalyst by impregnation, coprecipitation, or other suitablemeans. The titaniferous compound can be incorporated as titanium(IV)oxide or as a compound convertible to titanium(IV) oxide by calcination.The titaniferous compound can be incorporated before, at the same time,or after the incorporation of the tungsten compound into the silicasupport.

Representative examples of suitable titaniferous compounds (containingor yielding titanium) that can be used include:

Titanium(IV) oxide;

Titanium alkoxides of the general formula Ti(OR)₄, where R ishydrocarbyl, for example, titanium(IV) n-propoxide, titanium IVisopropoxide, titanium(IV) ethoxide, titanium(IV) n-butoxide,titanium(IV) 2-ethylhexoxide;

Titanium carboxylates such as titanium(IV) oxalate, titanium(IV)citrate, titanium(IV) cresylate;

Titanium acetylacetonate;

Titanium chelates, particularly alkanolamine titanates, e.g.,triethanolamine titanate, triethanolamine titanate chelate having theformula Ti(C₃ H₇ O)₂ [OC₂ H₄ N(C₂ H₄ OH)₂ ]₂. (This is available fromDuPont under the designation Tyzor TE);

Titanium halides, such as titanium(III) chloride, and titanium(IV)chloride,

and the like, and mixtures thereof.

Generally, the finished catalyst contains from about 0.1 to about 20,preferably from about 1 to about 10 weight percent of the titaniumcomponent calculated as titanium dioxide and based on the total weightof the tungsten oxide and the silica support.

To be effective in the present catalyst system, the above describedcomponents of the catalysts are activated at elevated temperatures,generally in flowing air. The activation or calcination of the catalystis accomplished at a temperature of from about 300° C. to about 800° C.for a period of about several minutes to several hours or longer. Aconvenient and economical treatment is a temperature in the range ofabout 400°-700° C. for 0.5 to about 20 hours or longer.

The calcined catalyst described above can be, if desired, furthersubjected to a high temperature treatment in a reducing atmosphere. Thetemperature range and temperature of contact can be the same as ued forcalcination with a treating gas such as carbon monoxide, hydrogen, andthe like. The activated catalyst is preferably cooled with an inert gassuch as nitrogen prior to use in the olefin reaction.

The promoted catalyst can be used in disproportionation reactions in aconventional manner. The reaction temperature can vary depending uponthe catalyst and feed(s) employed, but will be sufficient to effectdisproportionation. Typically, the disproportionation is carried out ata temperature in the range of about 20° to about 600° C.

The disproportionation reaction can be carried out by contacting theolefins to be disproportionated with the catalyst in the liquid phase orthe gas phase, depending on structure and molecular weight of theolefins, temperature and pressure.

Olefins applicable for use in the process of the invention arenontertiary, nonconjugated acyclic mono- and polyenes having at least 3carbon atoms per molecule including cycloalkyl, cycloalkenyl, and arylderivatives thereof; cyclic and polycyclic mono- and polyenes having atleast 4 carbon atoms per molecule including alkyl and aryl derivativesthereof; mixtures of the above olefins; and mixtures of ethylene and theabove olefins. Many useful reactions are accomplished with such acyclicolefins having 3-30 carbon atoms per molecule and with such cyclicolefins having 4-30 carbon atoms per molecule. Nontertiary olefins arethose olefins wherein each carbon atom, which is attached to anothercarbon atom by means of a double bond, is also attached to at least onehydrogen atom. Internal olefins are preferred.

Some specific examples of acyclic olefins suitable for reactions of thisinvention include propylene, 1-butene, 2-butene, 1-pentene, 2-pentene,1-hexene, 1,4-hexadiene, 2-heptene, 1-octene, 2,5-octadiene, 2-nonene,1-dodecene, 2-tetradecene, 1-hexadecene, 1-phenylbutene-2, 4-octene,3-eicosene, 3-hexene, 1,4-pentadiene, 1,4,7-dodecatriene,2-methyl-4-octene, 4-vinylcyclohexene, 1,7-octadiene,1,5,9,13,17-octadecapentaene, 8-cyclopentyl-4,5-dimethyl-1-decene,6,6-dimethyl-1,4-octadiene, and 3-heptene, and the like, and mixturesthereof.

Some specific examples of cyclic olefins suitable for the reactions ofthis invention are cyclobutene, cyclopentene, cycloheptene, cyclooctene,5-n-propylcyclooctene, cyclodecene, cyclododecene,3,3,5,5-tetramethylcyclononene, 3,4,5,6,7-pentaethylcyclodecene,1,5-cyclooctadiene, 1,5,9-cyclodecatriene, 1,4,7,10-cyclododecatetraene,6-methyl-6-ethylcyclooctadiene-1,4, and the like, and mixtures thereof.

The pressure during the disproportionation reaction may vary betweenwide limits. Pressures between 0.1 and 500 atm. are suitable; preferredpressures are between 0.5 and 250 atm. If possible, the process shouldbe operated at a pressure which is atmospheric or nearly atmospheric sothat no vacuum or pressure apparatus is required.

If the reaction is carried out in the liquid phase, solvents or diluentsfor the reactants may be used. Aliphatic saturated hydrocarbons (e.g.,pentane, hexane, cyclohexane, dodecane) and aromatic hydrocarbons suchas benzene and toluene are suitable. If the reaction is carried out inthe gaseous phase, diluents such as aliphatic hydrocarbons (e.g.,methane, ethane) and/or inert gases (e.g., nitrogen, argon) can bepresent. Preferably the disproportionation reaction is effected in thesubstantial absence of reactive materials such as water and oxygen.

The length of time during which the olefinically unsaturated compoundsto be disproportionated are contacted with the catalyst depends uponseveral factors such as the activity of the catalyst, temperature,pressure, and structure of the olefinically unsaturated compound to bedisproportionated. Contact time can conveniently vary between 0.1 secondand 24 hours, although longer and shorter contact times may be used. Thecontact time needed to obtain a reasonable yield of disproportionatedproducts depends on the factors mentioned above.

The process of the invention is effected batchwise or continuously, withfixed catalyst beds, slurried catalysts, fluidized beds or by using anyother conventional contacting technique. The solid disproportionationcatalysts are employed in any appropriate form, for example, as powders,flakes, pellets, spheres or extrudates.

The olefinic products of the invention, for the most part, haveestablished utility as precursors of polymers, e.g., as the thirdcomponent of ethylene-propylene terpolymers useful as syntheticelastomers. Cleavage of the ethylenic bonds of polyolefinic products asby ozonization produces di- or polycarboxylic acids which are reactedwith diamines, e.g., hexamethylenediamine, to form Nylons which areuseful in synthetic fibers. The olefinic products are converted tosecondary and tertiary alcohols as by sulfuric acid-catalyzed hydration.Alternatively, the olefinic products are converted by conventional "Oxo"processes to aldehydes which are hydrogenated with conventionalcatalysts to the corresponding alcohols. The C₁₂ -C₂₀ alcohols therebyproduced are ethoxylated as by reaction with ethylene oxide in thepresence of a basic catalyst, e.g., sodium hydroxide, to formconventional detergents and the lower molecular weight alcohols areesterified by reaction with polybasic acids, e.g., phthalic acid, toform plasticizers for polyvinyl chloride.

The following examples illustrate the invention.

EXAMPLE 1

Control catalyst preparation:

2.31 g ammonium metatungstate dissolved in 77 mL water was used toimpregnate 33 g silica (20-40 mesh size, low sodium, low alumina). Thewater was evaporated in air as the catalyst was dried over a hot plate.The material was then calcined in air at 500° C. to produce 6 wt% WO₃/SiO₂ catalyst.

Inventive catalyst preparation:

10 mL of a 1 molar aqueous solution of titanium (IV) citrate and 0.82 gammonium metatungstate dissolved in 50 mL water were combined and addedto 11.2 g silica. The catalyst was dried as above to produce 6 wt% TiO₂/6 wt% WO₃ /SiO₂ catalyst.

Comparative Catalytic Tests:

Tests for disproportionation/isomerization activity with propylene feedwere run in a quartz tube reactor with 1.5 g of catalyst supported byquartz wool in the center of the reactor which was heated in an electricfurnace.

Identical runs were made with the 6% WO₃ /SiO₂ control catalyst and withthe 6% TiO₂ /6% WO₃ /SiO₂ inventive catalyst described above. Eachcatalyst was heated 1 hr at 600° C. with air flowing at 200 mL/min, then1/2 hr with nitrogen flowing at 200 mL/min then the temperature waslowered to 400° C. to begin the test. Both runs were made withpolymerization grade propylene fed at 150 mL/min at atmosphericpressure. The catalyst temperature was maintained at 400° C. Effluentfrom the reactor was analyzed with a gas chromatograph. Several sampleswere taken during the 11/2 hr test for analyses. Averages for theseanalyses are presented in Table I.

                  TABLE I                                                         ______________________________________                                                       Propylene   Selectivity                                        Catalyst       Conversion, %                                                                             to 1-Butene, %                                     ______________________________________                                        6% WO.sub.3 /SiO.sub.2                                                                       16.6        0.6                                                6% TiO.sub.2 /6% WO.sub.3 /SiO.sub.2                                                         21.1        10.3                                               ______________________________________                                    

The yield of 1-butene provides a measure of the double bondisomerization activity of the catalyst. Ethylene and 2-butene are theprimary products of propylene disproportionation, and the 1-butene isproduced by isomerization of the 2-butene. Selectivity to produce1-butene with the inventive catalyst was much greater than with thecontrol.

EXAMPLE 2

Control Catalyst preparation:

Following a procedure similar to that of example I, a 10 wt% WO₃ /SiO₂catalyst was prepared. This is designated Catalyst 1.

Inventive catalyst preparation:

The same silica base used above was impregnated with an aqueous solutionof bis(triethanolamine)titanium diisopropoxide (Tyzor TE, a product ofE. I. du Pont de Nemours & Co., Inc. Wilmington, DE). The impregnatedsilica was dried at 400° C. for 1 hr. After cooling, thetitanium-impregnated silica was further impregnated with ammoniummetatungstate. After drying in air at 250° C. for 1 hr, the catalystcontained about 10 wt% tungsten oxide and 8 wt% titanium oxide onsilica. This is designated Catalyst 2.

Comparative Catalytic Tests:

Tests for disproportionation/isomerization activity with 1-hexene wererun in a vertical stainless steel tube reactor, 3/4" o.d.×14" long.Glass wool and glass beads were used to position the fixed bed ofcatalysts in the center of the reactor which was heated in an electricfurnace.

Comparative runs were made with the 10% WO₃ /SiO₂ control catalyst andwith the 8% TiO₂ /10% WO₃ /SiO₂ catalyst described above. For each run,0.7 g catalyst was activated by heating the bed at 550° C. in flowingair for 2 hr., then in CO for 30 min and cooling under argon flow toreaction test temperature. Both runs were made with 1-hexene purified bypumping it through beds of silica gel and MgO prior to entering theheated reactor. In each six hour run the reaction temperature wasincreased at one hour intervals. The pressure in the reactor was 50psig. The results are presented in the following table II.

                                      TABLE II                                    __________________________________________________________________________                                     Selectivity                                                     Temp.    1-hexene                                                                           C.sub.10 olefins,                                                                   Liquid Product Distribution (mole                                             %)                                     Run                                                                              Catalst         (°C.)                                                                      WHSV*                                                                              Conv. %                                                                            %     C.sub.5.sup.═                                                                C.sub.6.sup.═                                                                C.sub.7.sup.═                                                                C.sub.8.sup.═                                                                C.sub.9.sup.═                                                                C.sub.10.sup.═                                                               C.sub.11.sup..dbd                                                             .  C.sub.12.sup..                                                                dbd.              __________________________________________________________________________    1  10% WO.sub.3 /SiO.sub.2                                                                       298 40   11.2 75.5  0.6                                                                              88.8                                                                             0.8                                                                              0.2                                                                              0.6                                                                              8.46                                                                             0.2                                                                              0.04              2  8% TiO.sub.2 /10% WO.sub.3 SiO.sub.2                                                          296 41   14.8 43.2  1.8                                                                              85.2                                                                             2.4                                                                              1.0                                                                              1.9                                                                              6.4                                                                              0.5                                                                              0.1               3  10% WO.sub.3 /SiO.sub.2                                                                       350 39   34.5 62.7  2.2                                                                              65.5                                                                             3.3                                                                              1.2                                                                              3.2                                                                              21.6                                                                             1.6                                                                              0.4               4  8% TiO.sub.2 /10% WO.sub.3 /SiO.sub.2                                                         352 40   32.2 31.1  4.3                                                                              67.9                                                                             5.7                                                                              3.0                                                                              4.6                                                                              10.0                                                                             1.6                                                                              0.5               5  10% WO.sub.3 /SiO.sub.2                                                                       353 80   15.6 74.7  0.8                                                                              84.4                                                                             1.0                                                                              0.3                                                                              0.9                                                                              11.7                                                                             0.4                                                                              0.05              6  8% TiO.sub.2 /10% WO.sub.3 /SiO.sub.2                                                         348 78   20.4 43.5  2.3                                                                              79.6                                                                             3.1                                                                              1.3                                                                              2.6                                                                              8.9                                                                              0.9                                                                              0.3               7  10% WO.sub.3 /SiO.sub.2                                                                       397 41   47.7 48.7  4.1                                                                              52.3                                                                             6.3                                                                              2.8                                                                              5.9                                                                              23.2                                                                             2.8                                                                              0.7               8  8% TiO.sub.2 /10% WO.sub.3 /SiO.sub.2                                                         397 40   52.5 25.2  6.5                                                                              47.5                                                                             9.9                                                                              6.1                                                                              8.2                                                                              13.2                                                                             3.2                                                                              1.2               9  10% WO.sub.3 /SiO.sub.2                                                                       402 82   34.9 61.7  2.4                                                                              65.1                                                                             3.4                                                                              1.2                                                                              3.3                                                                              21.5                                                                             1.5                                                                              0.3               10 8% TiO.sub.2 /10% WO.sub.3 /SiO.sub.2                                                         403 82   35.6 35.9  4.2                                                                              64.5                                                                             5.9                                                                              2.9                                                                              5.1                                                                              12.8                                                                             1.9                                                                              0.6               11 10% WO.sub.3 /SiO.sub.2                                                                       449 81   49.0 45.3  4.5                                                                              51.0                                                                             7.1                                                                              3.2                                                                              6.4                                                                              22.2                                                                             2.8                                                                              0.6               12 8% TiO.sub.2 /10% WO.sub.3 /SiO.sub.2                                                         451 80   45.3 36.4  4.7                                                                              54.7                                                                             7.4                                                                              3.9                                                                              6.5                                                                              16.5                                                                             2.7                                                                              0.7               __________________________________________________________________________     *gm 1hexene/gm catalyst/hr (feed rate)                                   

Inspection of Table II shows that TiO₂ /WO₃ /SiO₂ catalyst causesgenerally higher conversion of 1-hexene than does the WO₃ /SiO₂catalyst. Ethylene and 5-decene are the primary products of 1-hexenedisproportionation. Thus data in Table II show for the WO₃ /SiO₂catalyst that C₁₀ olefin is the major product. The other C₅ through C₁₂liquid olefins produced are a result of isomerization. Comparison of thedata for the inventive catalyst to the control shows higher amounts ofC₅, C₇, C₈, C₉, C₁₁ and C₁₂ indicating enhanced isomerization with thetitanated WO₃ /SiO₂ catalyst.

We claim:
 1. A process for disproportionating and isomerizing olefins comprising contacting at least one feed olefin having at least three carbon atoms per molecule under suitable reaction conditions which convert the feed olefin into other olefins having different numbers of carbon atoms with a catalytically effective amount of a catalyst composition consisting essentially of silica and tungsten oxide promoted with an effective promoting amount of a titaniferous agent.
 2. A process according to claim 1 wherein said promoted catalyst is activated by heating to an elevated temperature under calcination conditions.
 3. A process according to claim 2 wherein said tungsten oxide is in the range of about 0.1 to about 30 percent of the combined weights of metal oxide and silica and said calcined catalyst is further heated at an elevated temperature in a reducing atmosphere.
 4. A process according to claim 3 wherein said olefin comprises propylene or 1-hexene and the reaction is carried out at a temperature in the range of about 20° C. to about 600° C.
 5. A process according to claim 4 wherein the titaniferous agent is employed in an amount in the range of about 0.1 to about 20 weight percent of the titanium component calculated as titanium dioxide based on the weight of the tungsten oxide-silica combination.
 6. A process according to claim 1 wherein the titaniferous agent is employed in an amount in the range of about 0.1 to about 20 weight percent of the titanium component calculated as titanium dioxide based on the weight of the tungsten oxide-silica combination.
 7. A process according to claim 6 wherein said titaniferous agent is titanium(IV) citrate or bis(triethanolamine)titanium diisopropoxide.
 8. A process according to claim 1 wherein said feed olefin contains ethylene. 